The NFL Players Association is investigating whether the Oakland Raiders violated league concussion protocol by letting quarterback Terrelle Pryor return to Monday night’s game after a blow to the head, Fox Sports reported Wednesday.

A source told ESPN.com that the Raiders’ conduct after Pryor’s hit in the fourth quarter of the game in Denver was “questionable.’’

Terrelle Pryor sustained a concussion in Monday night's game, but stayed on the field for a few plays after he was hit in the head. (AP photo)

Pryor lay on the field for several seconds after the head-on hit by the Broncos’ Wesley Woodyard on a running play by Pryor. Team trainers and doctors did not come onto the field to examine Pryor, Fox Sports reported. Once he recovered, he stayed in the game for two more plays.

Head coach Dennis Allen said on Tuesday that he did not check on Pryor until after the series was over, several minutes later. After the game, though, Allen had said that he had spoken to Pryor after the play and that the quarterback showed no signs of a concussion.

On Wednesday, Allen denied that the Raiders did anything wrong.

“I feel confident that we followed the protocol and did what we were supposed to do," Allen said. "I think we all understand the emphasis placed on player safety, specifically on this regard. We don’t ever want to put a player out there and put him in danger.

"We’re going to follow it and do what we’re supposed to do. It’s really a matter of, when the medical personnel feel like he’s fine and he’s cleared to practice and play, then he’ll be out there.’’

Asked by a Fox Sports reporter after the game if Pryor had seemed concussed after the play, Woodyard laughed, according to the report. Asked if that meant yes, Woodyard laughed again, said, "Nah, he didn't show any signs," then laughed again.

NFL policy for handling concussions includes a “mandatory” examination of the player after he is “slow to get up following a hit to the head, and immediate removal from the game if he suffers a hit that is likely to result in a concussion.

Coincidentally, the news of the NFLPA’s concern came the same day that the NFL released its annual health and safety report. Included is the addition for this season of “an unaffiliated neuro-trauma consultant” who “will be available to assist team medical staffs with the diagnosis and management of suspected concussions or spine injuries during games.’’

It is not clear whether the independent consultant was part of the evaluation of Pryor after he was hit.